求助一道英语基础题!

问题描述:

求助一道英语基础题!
_____ we were when we heard the news that our country won 51 gold medals at the Beijing Olympics!
A.What fun B.What a fun C.How happy D.How happily
为什么?

we were 后面要加形容词,所以要用对形容词的感叹句How不用What;happily 是副词不是形容词.